The biochemical regulation of the dopamine receptor was studied in vitro. Adenosine triphosphate (ATP) and adenylyl imidodiphosphate (AMPPNP), a non-hydrolyzable analogue of ATP, both enhance the binding of 3H dopamine to rat brain striatal tissue. Adenylate cyclase activity did not appear to be involved in this effect nor does Na+-K+ ATPase activity appear to be involved. Studies with sodium orthovanadate, however, suggest that a Ca+2 or Mg+2 ATPase may be involved.